Knowledge Base

Problem

The DanioVision TCU shows a 2-blink error LED pattern, or the temperature rises/falls abnormally slowly, suggesting air trapped in the coolant loop.

Details

Symptoms: Temperature increases very slowly to setpoint, overshoots, or behaves erratically over days of use. The 2-blink fault code is reported. Replacing the filter and refilling coolant alone does not resolve the fault, indicating residual air in the loop. Distinct from the 6-blink SD card fault (see related article).

Solution

1. First confirm the coolant reservoir is filled to the correct level with Noldus-approved coolant liquid (do not use water).
2. Replace the TCU filter if it has not been replaced recently.
3. If the fault persists after refilling and filter replacement, air is trapped in the coolant loop:
a. Turn the TCU switch to the 'Fill/Drain' (self-circulation) position.
b. Allow the unit to run in this mode; it will automatically purge trapped air from the loop.
c. Once purging is complete, return the switch to normal operating mode.
4. Monitor the temperature to confirm it stabilises at the correct setpoint.
5. If the controller continues to malfunction after purging, the temperature controller board may need replacement — contact Noldus support to arrange a spare controller or RMA.